An infrared sensor is used for a cooking device for example as a temperature sensor that measures the temperature of an object such as foodstuffs.
The method of correcting infrared sensor signals in PTL 1 has a first correction process and a second correction process. The first correction process includes a process of adding or subtracting offset correction amount A based on the environmental temperature. The second correction process is performed after the first one and includes a process of multiplying correction coefficient B based on the environmental temperature.
When infrared rays emitted from a measurement target reaches the infrared sensor unit, infrared sensor signal SIR corresponding to the amount of infrared energy is output as a voltage value.
In the first correction process, adding or subtracting offset correction amount A determined by the environmental temperature to or from infrared sensor signal SIR provides a first corrected signal. Here, offset correction amount A is a correction amount determined by the type of the infrared sensor unit of the infrared sensor device and by a function on the environmental temperature. Offset correction amount A is expressed by a function including terms of the third and/or second order.
Offset correction amount A is determined as follows. For example, the temperature of a measurement target at a constant temperature is measured under conditions with different environmental temperatures. Then, plotting environmental temperatures (the horizontal axis) and infrared sensor signals (the vertical axis) produces offset correction amount A as a function on the environmental temperature. In other words, offset correction amount A is determined at each environmental temperature.
Next, in the second correction process, multiplying the first corrected signal by correction coefficient B determined by the environmental temperature produces a second corrected signal that is substantially constant for environmental temperatures. Here, correction coefficient B is a coefficient that does not have a unit, and a signal that is the first corrected signal to or from which offset correction amount A is added or subtracted is multiplied by correction coefficient B.
Disclosure is made that two-step correction as described above is performed for correction based on the environmental temperature.
The temperature sensor in PTL 2 includes an infrared sensor, a thermistor, and a calculating unit. The infrared sensor is formed of a thermopile and converts thermal energy to electric energy. The thermistor measures the temperature of the infrared sensor. The calculating unit, formed of IC elements, computes the temperature of an object as a measurement target based on output voltages of the infrared sensor and the thermistor. This infrared sensor uses the thermistor to measure the temperature of the infrared sensor and corrects the output voltage of the infrared sensor based on the output voltage of the thermistor.